Project Summary The overall goal of this project is to ascertain the effect of a differential expression of alleles of human Apolipoprotein E (APOE) on synaptic physiology in cholinergic neurons as an animal ages. A variant of the gene APOE is the strongest genetic risk factor for Alzheimer?s disease (AD) the most common neurodegenerative disease. And although much has been uncovered about the role of APOE in the etiology of AD, the precise function of the protein in disrupting cholinergic neuron function remains unclear. Using the vast collection of molecular genetic tools and techniques available Drosophila, this project will test the effect of APOE alleles on function properties of cholinergic neurons. Through generous K01 Career Development support to this PI, our lab has developed the infrastructure and expertise to assay the synaptic physiological properties of cholinergic neurons. These resources enable us to conduct a pilot study to test the hypothesis that overexpression of human APOE4 but not APOE2 in cholinergic neurons causes deficits in synaptic physiology in Drosophila ACh neurons which are modified by age. In Specific Aim 1, we will determine the effect of a differential expression of APOE2 and APOE4 alleles on synaptic physiology in Drosophila. Specifically, we will determine the effect of each allele on neuronal excitability and presynaptic release using experimental procedures that we have optimized in our lab. In Aim 2, we will determine whether any effects of APOE on cholinergic neurons are modified by the aging process. We will first determine the effect of each APOE allele on Drosophila survivorship and on a metabolic marker of aging. We will then test the effect of each APOE allele on ACh neuronal excitability in aged Drosophila and compare those results with aged wildtype animals. These studies will provide critical preliminary evidence on the effect of APOE alleles on synaptic physiology and significantly advance our understanding of the role of a known AD risk factor in the etiology of the disease. The studies will also provide a platform for more comprehensive studies of the intrinsic properties of cholinergic neurons that lead to its selective susceptibility to neuronal loss in AD.